In the molding of plastics, change of a resin being used has conventionally necessitated various means for eliminating the influences of the preceding resin. Especially in the molding of colored resins, when the resin to be molded is changed from one of a dark color, e.g., blue or black, to one of a light color, e.g., white, a complicated cleaning operation has been necessary which comprises, for example, disassembling and cleaning the molding machine or purging the molding machine with a general or reclaimed resin or the like and is accompanied by a prolonged suspension of production. As a means for eliminating these problems, various thermoplastic resin compositions for purging molding machines have been developed.
For example, Unexamined Published Japanese Patent Application No. 62-195045 proposes a composition obtained by incorporating a sodium alkylbenzenesulfonate and a water-repellent compound (a metal salt of a higher fatty acid, wax, liquid paraffin, synthetic wax, etc.) into a thermoplastic resin in respective amounts of from 2 to 30% by weight and from 0.5 to 10% by weight based on the composition; Unexamined Published Japanese Patent Application No. 05-060768 proposes a composition obtained by incorporating the calcium salt of a boric ester of a higher fatty acid monoglyceride and an inorganic filler into a thermoplastic resin; and Unexamined Published Japanese Patent Application No. 03-283805 proposes a purging composition obtained by incorporating a neutral salt of an alkylbenzenesulfonic acid and basic magnesium stearate into a thermoplastic resin in respective amounts of from 2 to 40% by weight and from 1 to 10% by weight based on the composition.
However, the conventional purging compositions described above are still insufficient in cleaning ability, and there is a desire for a thermoplastic resin composition for purging which has a high cleaning ability.
As apparent from the above description, an object of the present invention is to provide a thermoplastic resin composition for purging a molding machine, which has an excellent cleaning ability.